Enhanced summertime background ozone by anthropogenic emissions – Implications on ozone control policy and health risk assessment

Abstract

Quantifying background ozone (O3-BG) is critical for emission control policy development due to its significant contribution to the overall O3 levels. However, O3-BG is still hard to monitor because of the universal existence of human activities and the complex interactions between anthropogenic and biogenic emissions. Here, we used a source-oriented chemical transport model to assess O3-BG with (O3-BG-anth) and without (O3-BG-ult) the presence of anthropogenic emissions. Results show that anthropogenic emissions enhance O3-BG-anth compared to that derived from biogenic emissions alone (O3-BG-ult). The enhancement increases with increasing O3 levels because anthropogenic emissions generally increase abundance of OH and HO2 radicals, raising atmospheric oxidation capacity. Sensitivity analysis demonstrates that anthropogenic NOx abatement could have the co-benefit of reducing biogenic O3, leading to more effective O3 pollution control. In contrast, reducing anthropogenic VOCs increases the production of biogenic O3, which is not beneficial to overall O3 reduction. Our findings provide valuable information for developing emission control policy and risk assessment.